Control apparatus of internal combustion engine

Abstract

The ignition timing is sustained at an initial value during a predetermined time beginning at a start of an engine, and is retarded after the predetermined time is elapsed to heat a catalyst at an early time. The predetermined time ends when the negative pressure of an intake pipe or the negative pressure of a brake booster reaches to a predetermined value. That is, the predetermined time is a period, which begins at a start of the engine and ends when a proper negative pressure can be sustained in the brake booster. As a result, it is possible to assure a negative pressure in the brake booster at an early time and to reduce exhaust emission at a start of the engine simultaneously.

Description

[0001] This application is based on Japanese Patent Applications No. 2001-153412 filed on May 23, 2001, and No. 2001-223436 filed on Jul. 24, 2001 the contents of which are incorporated herein by reference.[0002] 1. Field of the Invention[0003] The present invention relates to a control apparatus of an internal combustion engine.[0004] 2. Related Art[0005] A car manufactured in recent years is provided with a catalyst such as a three-way catalyst, which is used for purifying exhausted gas, on the exhaust pipe of the car. At a cold start in which the engine is started at a low temperature of the engine and the catalyst, the ignition timing is retarded to increase the temperature of the exhausted gas. The increased temperature of the exhausted gas in turn promotes the heating of the catalyst so that the temperature of the catalyst is increased to a value in an active temperature range at an early time.[0006] If the ignition timing is retarded in order to heat the catalyst at an early ...

AI Technical Summary

Benefits of technology

[0013] It is a further object of the present invention to provide an internal combustion engine with a control apparatus capable of assuring a negative pressure required by a brake unit at a start time of the engine and at a time immediately following the start time.

[0022] In accordance with a still further aspect of the present invention, the ignition timing's retardation quantity and / or retardation speed are set on the basis of a sum of differences between negative pressures recognized by the negative pressure recognizing means and a predetermined value or a maximum value of the differences. With the ignition timing's retardation quantity and / or retardation speed set in this way, the negative pressure of the brake booster can be lowered to a proper negative pressure level in a short period of time by reducing the retardation quantity of the ignition timing and / or lowering the retardation speed of the ignition timing when the actual negative pressure of the brake booster is determined to be insufficient as indicated by a small sum of differences between negative pressures recognized by the negative pressure recognizing means and the predetermined value or a small maximum value of the differences. On the other hand, a large sum of differences between negative pressures recognized by the negative pressure recognizing means and the predetermined value or a large maximum value of the differences indicates that the negative pressure in the intake pipe (or the negative pressure of the brake booster) is sufficiently low, leading to a determination that a proper negative pressure of the brake booster can still be assured even if the negative pressure in the intake pipe slightly rises so that the catalyst heating effect based on retardation of the ignition timing can be enhanced by increasing the retardation quantity of the ignition timing and / or raising the retardation speed of the ignition timing in a range that does not deteriorate the combustibility.

Problems solved by technology

If the ignition timing is retarded in order to heat the catalyst at an early time, however, the engine torque decreases.

At a cold start, however, the fuel stability of the engine is poor so that, if the ignition timing is much retarded from the cold start as is the case with the disclosed technology, the fuel condition becomes unstable, unavoidably increasing the quantity of an exhausted unburned gas component such as HC or CO.

In addition, if the ignition timing is much retarded from the cold start, the retard angle for the ignition timing causes a delay of the decreasing of the intake manifold negative pressure.

In the mean time, the negative pressure of the brake booster cannot be assured at a sufficient value so that the performance of the brake booster cannot be fully displayed.

In short, with the disclosed technology, it is difficult to assure a sufficient negative pressure of the brake booster while reducing the exhaust emission at a start of the engine at the same time.

By execution of advancing control on the VVT in accordance with reduction of the negative pressure, however, the state of combustion cannot be improved sufficiently.

In addition, if the ignition timing is retarded in order to heat the catalyst at an early time, the resulting negative pressure is not sufficient as described above.

Thus, with the technology disclosed in U.S. Pat. No. 3,129,802, advancing control is executed on the VVT in accordance with a negative pressure signal, resulting in an unimproved state of combustion.

Caused by deterioration of a combustion state at a start of the engine, the generation of unburned gas components is the main cause of deterioration of emission at the start of the engine.

In this case, during a period of time beginning from a start of the engine, the retardation speed of the ignition time is low, resulting in a small retardation quantity.

When the brake is applied next with the negative pressure expended, the driver needs to apply a large depressing force, which causes a feeling of incompatibility in the driver.

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